Fifth wheel construction



Dec. 19, 1961 H. A. GEERDS FIFTH WHEEL CONSTRUCTION 3 Sheets-Sheet 1 Original Filed April 27, 1959 w w a. W m

m 5 a W mg E "a w W Wm H a Y FIG. 3

ATTORNEYS Dec. 19, 1961 H. A. GEERDS 3,013,815

FIFTH WHEEL CONSTRUCTION Original Filed April 27, 1959 5 Sheets-Sheet 2 26 6o I 42 35 INVENTOR HER/WAGEEEDS BY QM #W Dec. 19, 1961 H. A. GEERDS FIFTH WHEEL CONSTRUCTION Original Filed April-27, 1959 3 Sheets-Sheet 3 Hf/v/emezz g BY {'W ATTORNEYS 3,013,815 Patented Dec. 19., 1961 huh 3,tl13,315 FilFTH WlmEL CONSTRUCTION Henry A. Geerds, Holland, Mich, assignor to Holland Hitch fjompany, Holland, Mich, a corporation of Michigan Griginal application Apr. 27, 1959, Ser. No. 809,255, now Patent No. 2,982,566, dated May 2, 1961. Divided and this application July 11, 1960, fier. No. 42,174

7 Claims. (Cl. 280-435) This invention relates to fifth wheels. More particularly, it relates to an improved king pin engaging assembly for fifth wheels. I

This application is a division of my co-pending application Serial No. 809,255, filed April 27, 1959, and now Patent No. 2,9825 66, entitled Fifth Wheel.

It is conventional practice to couple a truck trailer to a truck or tractor therefor by means of a locking pin or king pin and a so-called fifth wheel. Normally the king pin is carried on the underside of the front portion of the trailer while the fifth wheel is mounted on top of the back frame of the tractor. The fifth wheel generally comprises a main plate which supports the front end of the trailer and a king pin engaging assembly. A typical exampie of fifth wheel and one on the basis of which this invention is an improvement is shown and described in U.S. Patent No. 2,348,977 to Henry Ketel.

The king pin engaging assembly usually comprises king pin coupling means and locking means for holding the coupling means in king pin coupling position. With the locking means in unlocked position the king pin is usually moved in and out of the king pin engaging assembly by backing the tractor into position under the trailer and by moving the tractor forward from the trailer.

A disadvantage of the previous types of king pin engaging assemblies resides in the rather complex structures and, hence, the large number of working parts involved. It is axiomatic that the greater the number of working parts in a structure the greater are the chances of failure and the greater the cost of manufacture.

Another major disadvantage of previous types of king pin engaging assemblies is that they will couple and lock on an improperly seated king pin. If, for one reason or another, the king pin enters the fifth wheel at too high an elevation relative to the king pin engaging assembly while the tractor is being backed up to the trailer, the king pin may enter the king pin engaging assembly and be coupled and locked horizontally. However, the structure of this type of king pin engaging assembly is such that the king pin may not be coupled and locked vertically. This improper coupling gives rise to a very serious and real danger that upon the tractor or trailer striking a bump in the road and the like under use conditions, the sudden downward motion of the fifth wheel relative to the king pin or the sudden upward motion of the king pin may cause the king pin to pop out of the king pin engaging assembly.

A general object of this invention is to provide an improved king pin engaging assembly.

A particular object of this invention is to improve the king pin engaging assembly over previous arrangements.

A specific object of this invention is to obtain this improvement with a simplified structure and a minimum number of working parts.

Another general object of this invention is to provide a king pin engaging assembly-having structure with built-in safety features.

These and other objects which may appear as this specification proceeds are achieved by this invention which shall be described with reference to the drawings which form a material part of the disclosure. A brief description of the drawings is as follows.

FIG. 1 is a plan view of a preferred embodiment of the improved fifth wheel of this invention, the main plate of which has been partially removed to reveal internal structure of the king pin engaging assembly.

I FIG. 2 is a side sectional view of the fifth wheel taken along the line Z.2 of FIG. 1.

FIG. 3 is a cross sectional view taken along the lines 3-3 of P16. 1 but with the king pin expelled from the king pin engaging assembly.

FIG. 4 is a bottom view of the central portion of the fifth wheel assembly of FIG. 1, which view displays a king pin seated in the king pin engaging assembly shown in 7 locked condition.

FIG. 5 is a front partially sectional view illustrating position of the outer functional release handle member of the king pin engaging assembly when the same is in the condition illustrated in FIG. 4.

FIG. 6 is a bottom view of the central portion of the fifth Wheel assembly of FIG. 4, but with the king pin engaging assembly shown in unlocked but closed condi tion.

FIG. 7 is a front, partially sectioned, view showing the position of the outer functional portion of the release handle member of the king pin engaging assembly when the assembly is in the condition displayed in FIG. 6.

FIG. 8 is a bottom view of the central portion of the fifth wheel assembly of FIG. 6, but with the king pin engaging assembly in unlocked and open condition and with the king pin expelled.

FIG. 9 is a side sectional view of the fifth wheel taken as though along the lines 22 of FIG. 1, but showing the king pin engaging assembly in unlocked and open condition with the king pin positioned forwardly of the assembly at the proper height for coupling and showing in phantom a king pin at too high an elevation relative to the fifth wheel for proper coupling.

FIG. 10 is a front view of the central portion of the fifth wheel taken along the section line INF-10 of FIG. 1 but with the king pin removed and the king pin engaging assemb y in unlocked and open condition.

These drawings show broadly a fifth wheel of the type taught in the Ketel patent but with certain improvements in structure and function.

One of the structural concepts generally disclosed in the drawings is a yoke retraction assembly involving a roller pin member of the yoke disposed in a transverse.

prises spring means which urge the release rod means into lock position. I

Another structural concept generally disclosed in the drawings is that of means for preventing the king pin coupling portion of the king pin engaging assembly from closing and partially coupling a king pin disposed in the.

assembly at too high an elevation for being coupled against vertical movement.

Structure The drawings specifically disclose a fifth wheel which comprises a generally horizontal main plate 14 and a king pin engaging assembly 15.

The main plate 14 is mounted on brackets 16 and 17 which are normally secured to the back end of the truck or tractor. Centrally disposed in the main plate 14 is a king pin receiving slot 18 which merges into a V-shaped entrance 19. The fifth wheel will usually be mounted on the tractor so that the entrance 19 faces rearwardly of the tractor whereby, when the tractor is backed up to the trailer, the king pin can enter into the slot 18. For

the purpose of simplicity in description, however, the king pin receiving end of the fifth wheel 12 will be regarded as the front end of the fifth wheel 12 so that on this basis the entrance 19 is located forwardly of the king pin receiving slot 18. The underside of the main plate 14 comprises a pair of rib members 20 and 21 disposed on each side of the slot 18 generally parallel to one another. Rearwardly of the slot 13 and secured to the bottom side of the rib members 26 and 21 is a transverse support plate 23. Along the back of the main plate 14, there is provided a downwardly extending flange member 22. Other supporting rib members such as indicated by the numeral 49 in FIGS. 1 and are also provided on the underside of the main plate 14.

The king pin engaging assembly comprises a pair of king pin coupling jaws 24 which are pivotally mounted rearwardly of the king pin receiving slot 18 on pivot pins 25 perpendicularly mounted on and between the main plate 14 and support plate 23. Forwardly of the pivot pins 25, the king pin coupling jaws 24 are provided with semi-circular, oppositely disposed, lateral recesses and projections, which are adapted to laterally conform to the lower portion of a king pin 26 when it is at the proper height relative to the fifth wheel 12.

King pins are generally cylindrical in shape. However, in the region of the bottom thereof, as shown in FIG. 2, there is an annular recess 27 below which is a collar 28. When the king pin 26 is at proper height relative to the fifth wheel 12 and disposed in the slot 18 and when the jaws are in closed position the semi-circular recesses and projections of the jaws 24 will abut and hub the upper cylindrical portion of the king pin 26 and the inside of the annular recess 27. The collar portion 28 will be on the underside of the jaws 24.

Each of the jaws 24 at the forward end thereof cornprises a laterally extending member or dog 29. Opposite the dog 29, the ribs 20 and 21 are provided with apertures 30 to enable the front ends of the jaws 24 to move outwardly laterally upon uncoupling a king pin 26 from the fifth wheel 12. On the forward face of each jaw 24, there is provided a forwardly extending stop member 31 which engages the forward wall of the rib adjacent the aperture when each jaw 24 opens and thereby limits the outward lateral travel of the front end of each jaw 24. Rearwardly of their pivot points the coupling jaws 24 have laterally projecting portions 32 (FIGS. 1 and 4) which, in the embodiment shown, are in substantial alignment with the corresponding lateral portions of the jaw dogs 29. These rearwardly located laterally projecting portions 32 limit the extent of inner travel of the forward portion of the jaws 24. This extent at most should be the longitudinal centerline of the slot 18 and thus of the fifth wheel 12.

The king pin engaging assembly 15 in addition to the king pin coupling portion thereof, comprises a locking portion. This portion comprises a generally U-shaped yoke member 33 having generally parallel, forwardly extending leg members 34 which are positioned laterally of the jaws 24. Rearwardly of the jaws 24, the yoke 33 comprises a cross piece member 35 joined to the legs 34 and generally disposed in the same plane as the legs 34. The cross piece member 35 is also joined to a longitudinal bar member 36 disposed generally in the same plane and extending rearwardly therefrom through an opening 37 in the rear flange member 22 of the main plate 14. Rearwardly of the flange member 22 the bar member 36 is provided with threads and threadedly engaged therewith an adjusting nut 38. Between the adjustment nut 38 and the flange member 22 there is provided a resilient washer 39. Coiled about the bar 36 between the flange member 22 and the cross piece member 35 is a tension spring 40 which urges the yoke 33 forwardly. At the juncture of the bar member 36 with the cross piece member 35 of the yoke 33 and joined thereto is a downwardly extending roller pin member 42. The roller pin member 42 extends through a cam slot 43 in a cam plate 44.

The cam plate 44 is disposed generally horizontally. The rearward end thereof is pivotally secure rearwardly of the slot 43 to a pivot pin 45 carried by the main plate 14. Forwardly of the cam slot 43 the cam plate is provided with a hole for receiving a bent terminal portion of a laterally extending release rod 46. The cam slot 43 is transversely disposed through the cam plate 44. It is arcuate in shape, having a transverse center line on an arc with its center rearwardly of the cam plate 44. Consequently, an outward pull on the release handle 46 and thus movement of the cam plate 44 causes a rearwardly directed force component to be exerted on the roller pin 42 whereby the yoke 33 is moved rearwardly against the tension of the spring 40.

The transverse cam slot 43 comprises a forwardly directed pocket 47 at the end thereof in which the yoke roller pin 42 seats when the yoke 33 is rearwardly moved. The cam slot 43 also comprises a rearwardly directed pocket 48 at that portion thereof at which the yoke roller pin 42 is positioned when the yoke 33 is in lock position.

The locking portion of the king pin engaging assembly 15 also comprises a laterally and generally horizontally disposed release rod 46. The release rod 46 extends from the cam plate 44 through passageways 52 in the outer supporting rib members 49 of the main plate 14 to one side of the fifth wheel 12. This is most clearly shown in FIG. 1. The terminal portion of the release rod 46 outside of the fifth wheel 12 has a handle portion to facilitate manual manipulation of the rod. The release rod 46, between its juncture with the cam plate 44 and its passage through the main plate supporting rib structure 49, comprises a tension spring 50 which is attached at one end as shown in FIG. 1 by conventional means to the release rod 46 and which, at its opposite end, bears against the supporting rib structure 49 to bias the release rod 46 and cam plate member 44 into lock position. The release rod 46 is also provided with a downwardly projecting stud 51 which, when the release rod 46 is in the lock position as shown in FIG. 5, abuts the inner side of the supporting rib structure wall 49 about the release rod opening 52 therethrough. The abutting face of the stud 51, it will be observed, is perpendicular to the rod 46. The other end of the stud 51 is at an oblique angle to the rod 46.

While the supporting rib members 20 and 21 on each side of the king pin receiving slot 18 of the main plate member 14 have been described as generally parallel to one another it will be observed that in the region of the apertures 50 therethrough, the inside walls thereof are thickened inwardly to form inwardly directed tapers 54 and 55. In addition, although not necessary, the front ends of the legs 34 of the yoke 33 are tapered and transversely thickened. When the yoke member 33 is in locked position, the forward ends of legs 34 thereof will bear against the tapers 54 and 55. By means of these tapers and by adjustment of the adjustment nut 38 on the end of the longitudinal rod member 36, compensation can be made for lock wear.

The rearward portion of each dog portion 29 of the jaws 24 comprises a transverse cam surface 56 having a general are of curvature with the radial point thereof in the region of the pivot pin 25 of the corresponding jaw 24. When the king pin engaging assembly 15 is unlocked and the king pin 26 is uncoupled therefrom, the end of each of the yoke legs 34 is brought to bear against the corresponding cam surface 56 of each jaw 24. Further lateral movement of the jaws 24, due to the uncoupling action of the king pin 26, causes the jaw dog cam surfaces 56 to earn the yoke legs 34 rearwardly.

The fifth wheel 12 is also provided with means for preventing the jaws 24 from closing when a king pin 26 enters the slot 13 at too high an elevation relative to the jaws 24. Such means comprise a spring biased, pivoted, block 58, the upper portion of which spans the gap below the inner semi-circular projection between the jaws 24 when the jaws are infully openposition andthe king pin 26 is out of the slot 18 or, if it is in the slot 18, it

is at too high an elevation for proper coupling. The block the corresponding laterally extendingpins'on each side of the lower portion of the block 58 and brought the bear against the underside of the crossbar 60 between the ribs 20 and 21. The spring 62 biases the upper portion of the block 58 upwardly into its spanning position between the jaws 24 (FIG. 9).

Operation To prepare the fifth wheel 12 for receiving and for engaging a king pin 26, the following procedure is used.

The handle of the release rod 46 is lifted until the stud 51 thereof is within the area of the release rod slot 52. The rod 46 is then pulled out as far as it will go. This places the stud 51 on the other side of the supporting rib 49 (FIG. 7). This causes the cam plate 44 to move 7 laterally and thereby force the yoke roller pin 42 and thus the yoke 33 rearwardly to unlock position (FIG, 6). The yoke roller pin 42, because of the tension of the spring 40 on the longitudinal rod 36, will seat in the cam slot pocket 47. Because of the generally greater tension of the spring 40'relative to the release rod spring 5'0, seating of the roller pin 42 in the cam slot pocket 47 prevents the cam plate 44 and release rod 46 from returning to their initial position. The jaws 24 are now unlocked and can be opened.

The jaws 24 are opened by the withdrawing of the king pin and the jaw dogs 25 enter the apertures 30 in the supporting ribs 20 and 21. Movement of the jaws 24 into the apertures 30 and hence contact of the ends of the yoke legs 34 with the jaw dog cam surfaces 56 causes the yoke 33 to be moved rearwardly to retract position (FIG. 8), as the yoke 33 moves rearwardly the pressure of spring 40 is overcome somewhat and the pressure of spring 50 causes the yoke roller pin 4-2 to move from the cam slot pocket 47 and into position for movement in the cam slot 43. Because of the tension of the release rod spring 50, the release rod 46 and cam plate 44 are returned to their initial position, leaving the yoke roller pin 42 in position in the slot 43 for seating in the cam slot pocket 48. Movement of the jaws 24 into the apertures 30 to the limits imposed by the top members 31 also releases the block 53 from its lowered position and the upper portion thereof swings up to span the gap between the now open jaws 24.

To couple a king pin 26 to the fifth wheel 12, the tractor .on which the fifth wheel 12 is mounted is backed up to the trailer carrying the king pin until the king pin 26 enters the V-shaped entrance 19 of the main plate 14, and finally enters the slot 18.

If the king pin 26 is at the proper height relative to the jaws 24, that is, if the annular recess 27 i aligned with the corresponding portion of the lateral recesses of the jaws 24, as shown in FIG. 9, as the king pin 25 enters the slot 18, it knocks the block 58 down below the jaws 24 and holds it down until the king pin is withdrawn from the slot 18.

When the rear section of the recessed portions of the jaws 24 contact the king pin 26, they are compelled to move rearwardly. This causes the front portions of the jaws 24 to swing inwardly into coupling position and to close. The dog portions 29 of the jaws 24, of course,

move inwardly with the jaws 2 thus causing the ends of the yoke legs 34 to slide over the jaw dog cam surfaces 56. The yokelegs 34 are thereupon freeto move forwardly and, because the yoke roller pin 42 has already been unseated from the cam slot pocket 47 andbecause of the tension of the main spring 4%, the yoke 33 automatically moves forwardly to the limit imposed by the adjustment nut 38, which limit is that whereat the legs 34 block the apertures wand bear against the jaws 24. This locks the jaws 24 in coupling position about the king pin 25. At the same time, because of the tension of springs 40 and 50, the cam plate 44 and release rod 46 move back to their initial position, the stud 51 on the release rod 46 slipping over the rib 49 and dropping down into abutment with the innerside thereof. The yoke roller pin 42 seats in the cam slot pocket 48 whereby, in the event of failure of the longitudinal rod spring 40, inadvertent retraction of the yoke 33 is prevented.

If the king pin 26 is at too high an elevation relative to the jaws 24, that is, if the annular recess 27 is aligned with the upper portions of the jaws 24 corresponding to the cylindrical portion of the king pin 26 above the annular recess 27, as illustrated by the king pin in phantom View in FIG. 9, as the king pin enters the slot 18, it will not knock the block 58 down below the jaws 24. Consequently, while the rear sections of the recessed portions of the jaws 24 may strike the king pin 26, the front portions of the jaws are blocked from closing by the block 58.

To uncouple a king pin 26 from the fifth wheel 12, the handle on the release rod 46 is lifted until the stud 51 is within the area of the release handle passageway 52 through the supporting rib structure 49. The release rod 46 is then pulled out as far as it will go, thereby retract ing the yoke 33 into unlock position, shown in FIG. 6, and unlocking the jaws 24. In this position, the yoke roller 42 becomes seated in the cam slot pocket 47. The

tractor is then driven away from the trailer, thereby causing the king pin 26 to open the jaws 24 and be expelled. Opening of the jaws 24 causes further retraction of the yoke 33 to retract position because of the yoke legs 34 riding on the jaw dog cam surfaces 56. This unseats the yoke roller pin 42 from the cam slot pocket 47, as shown in FIG. 8, whereupon because of the tension of the release handle spring 59 the cam plate 3- 4 is pivoted, bringing the yoke roller pin 42 into position for seating in the cam slot pocket 48.

Thus there is provided a fifth wheel structure in which the construction has been simplified, operation simplified, and which contains safety features.

In all respects, the king pin engaging assembly is mechanically positive and, if inoperative because of a bent king pin, provides visual evidence of inoomplete coupling. This evidence resides in the position of the handle of the release rod 4-6 (FIG. 1) and the positions of the adjustment nut 38 and resilient washer 39.

The king pin engaging assembly of this invention cannot lock until the king pin has been encircled by the jaws. It cannot couple the king pin ifthe king pin is in a position too high with respect to the jaws. The engaging assembly cannot become unlocked in use except by a manual operation which starts the unlocking cycle. Every movlng part of the assembly is controlled throughout the unlocking procedure and coupling procedure and is held in proper position by spring tension.

The cam slot pocket 48 with the yoke roller pin 42 seated therein functions as a secondary means for holding the king pin engaging assembly in locked position should either or both of the release rod 56} and the main spring 44) rupture or otherwise fail. Without the cam slot pocket 48 and under use conditions, vibration could move the yoke to unlock position in the absence of the spring forces of these springs. The cam slot pocket 48 prevents this possibility from occurring.

Moreover, the king pin engaging assembly has an adjustable feature. Extent of forward travel of the yoke 33 can be regulated by the adjustment nut 33 (FIG. 1) even when the yoke is in lock position. Further, the rubber washer 39 (P16. 2), being resilient, provides a rebound against yoke travel, which minimizes wedging action resulting in a sticky lock. The type of adjustment invoived here increases the life of the jaws by removing all chucking action.

Still another feature of advantage of the king pin engaging assembly of this invention resides in the cooperation between the yoke legs 34- and the jaws 24. Under normal operative conditions and in the absence of the block 58 or with failure of the block spring 62, the contact between the ends of the yoke legs 34 and the cam surfaces 56 on the jaw dogs 29, which form holding pockets for the ends of the yoke legs, is sufficient because of the spring forces of the springs 40 and 5-1), which hold the ends of the legs in the pocket, to hold the jaws in open, king pin receiving position until a king pin enters the slot 18 and strikes the rearward portions of the jaws 24. Hence, inadvertent closure of the jaws 24 before receiving a king pin 26 is prevented. Moreover, under such conditions and in the event only the end of one leg 34- is in contact with a cam surface 56 of one jaw 24, the rearwardly located, laterally projecting portion 33 on the other jaw in combination with the corresponding leg 34 (the one out of contact with a jaw dog cam surface 56) limits the extent of inner movement of the forward portions of the jaw 24. Hence, obstruction of the king pin passage by a loose jaw 24 is prevented.

These and other features and advantages of this invention will be apparent to those of ordinary skill in the art upon reading the foregoing description. Moreover, this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof. The embodiment just described is, therefore, illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within the metes and bounds of the claims, or that form their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

I claim:

1. A fifth wheel comprising: a main plate having a centrally disposed king pin receiving slot; a king pin receiving assembly including a pair of jaw means pivotally connected to said plate and adapted to be opened to receive a king pin and to close to retain a king pin, a yoke reciprocally carried by said main frame and having legs, spring means urging said yoke to a forward position, cam portions on said legs engaging said main plate and said jaws and locking them in a closed position, and stop means for limiting the forward movement of said yoke to prevent jamming of said legs and being adjustable to compensate for wear between said jaws and said yoke; said stop means including an element with an adjusting member thereon adapted to operatively engage said main frame for limiting forward movement of said yoke, said adjusting member being movable to compensate for wear of said cam portions on said legs.

2. A fifth wheel comprising: a main plate having a centrally disposed king pin receiving slot; a king pin receiving assembly including a pair of jaw means pivotally connected to said plate and adapted to be opened to receive a king pin and to close to retain a king pin, a yoke reciprocally carried by said main frame and having legs, spring means urging said yoke to a forward position, cam portions on said legs engaging said main plate and said jaws and locking them in a closed position, said jaws including projections formed therewith and projecting laterally of said pivotal connections with said main plate, said projections engaging said yoke upon said jaws being closed and limiting the extent of closure thereof.

3. A fifth wheel for a tractor comprising: a pair of jaws pivotally connected to a main plate for releasably engaging a king pin, said jaws being closed by entry of said king pin therebetween, a yoke operative upon closing of said jaws to lock said jaws in a closed position, release means for moving said yoke to unlocked position and latch means for holding said release means in the unlocked position against first bias means applied to said yoke means, cam means on said jaws engaging said yoke when said jaws are opened by said king pin to permit release of said latch means, said main plate having leg engaging cam portions, said yoke having legs bearing cam surfaces for wedging said legs between said jaws and said leg engaging cam portions of said main plate when said yoke is moved to locked position; means for preventing movement of said yoke to locked position while said jaws are open; second bias means applied to said release means for releasing said latch means when said jaws are fully opened to set up said yoke for automatic movement to locked position when said jaws are closed by said king pin; and adjustable stop means asso ciated with said yoke and main piate for limiting movement of said yoke toward locked position so as to prevent excessively tight wedging of said yoke between said jaws and said main plate and so as to compensate for wear of said leg bearing cam surfaces and leg engaging cam portions.

4. A fifth wheel as in claim 3 wherein said release means includes a pivotally mounted cam plate having an arcuate cam slot, said yoke having a roller operable in said cam slot, a pocket formed in said slot and being aligned with said roller when said yoke is in its locked position, unlocking movement of said yoke in a manner other than by said release means causing said roller to enter said pocket and latch said release means against pivotal movement,

5. A fifth wheel for a tractor as in claim 3 wherein said release means includes an actuator element for actuation thereof, said actuator element having a detent engageable with stop on the tractor for locking said release means against releasing movement.

6. A fifth wheel for a tractor comprising: a pair of jaws pivotally connected to a main plate for releasably engaging a king pin, said jaws being closed by entry of said king pin therebetween, a yoke operative upon closing of said jaws to lock said jaws in a closed position, release means for moving said yoke to unlocked position and latch means for holding said release means in the unlocked position against first bias means applied to said yoke means, cam means on said jaws engaging said yoke when said jaws are opened by said king pin to permit release of said latch means, said main plate having leg engaging cam portions, said yoke having legs bearing cam surfaces for wedging said legs between said jaws and said leg engaging cam portions of said main plate when said yoke is moved to locked position; means for preventing movement of said yoke to locked position while said jaws are open; second bias means applied to said release means for releasing said latch means when said jaws are fully opened to set up said yoke for automatic movement to locked position when said jaws are closed by said king pin; and adjustable stop means associated with said main plate and yoke for limiting movement of said yoke toward locked position so as to prevent excessively tight wedging of said yoke between said jaws and said main plate and so as to compensate for wear of said leg bearing cam surfaces and leg engaging cam portions; said release means includes a pivotally mounted cam plate having an arcuate cam slot, said yoke having a roller operable in said cam slot, a pocket formed in said slot and being aligned with said roller when said yoke is in the locked position, unlocking movement of said yoke in a manner other than by said release means causing said roller to enter said pocket and latch said release means against pivotal movement; and said release means having actuator element for actuation thereof, said actuator element having a detent engageable with a stop on the frame for further locking said release means against movement.

7. A fifth wheel comprising: a main plate having a centrally disposed king pin receiving slot; a king pin re ceiving assembly including a pair of jaw means pivotally connected to said plate and adapted to he opened to re ceive a king pin and to close to retain a king pin, a yoke reciprocally carried by said main frame and having legs, spring means urging said yoke to a forward position, cooperating cam portions on the ends of said legs and on leg engaging portions of said main plate, said ends of said legs also engaging said jaws on the opposite side thereof of said leg engaging portionsof said frame and locking said jaws in a closed position; a stop element operatively secured to said yoke and adapted to operatively engage said main frame for limiting forward movement of said yoke; and adjustment means for adjusting the 15 position of, said yoke when said stop element operatively engages said main frame whereby the limited forward movement of said yoke can be adjusted to, prevent jam ming of said legs between said main plate and jaws and 5 to compensate for wear of said cam portions.

References Cited in the file of this patent UNITED STATES PATENTS 2,469,279 Seyferth May 3, 1949 2,663,575 Ketel Dec. 22, 1953 2,861,818 Kayler et a1 Nov. 25-, 1958 FOREIGN PATENTS 519,561 Belgium May 15, 1953 

